<?php
/*
| Author: Yang Yu <niceses@gmail.com>
| @param char|int $start_date 一个有效的日期格式，例如：20091016，2009-10-16
| @param char|int $end_date 同上
| @return 给定日期之间的周末天数
*/
function get_weekend_days($start_date,$end_date, $is_workday = false){
    if (strtotime($start_date) > strtotime($end_date)) 
        list($start_date, $end_date) = array($end_date, $start_date);
    $start_reduce = $end_add = 0;
    $start_N = date('N',strtotime($start_date));
    $start_reduce = ($start_N == 7) ? 1 : 0;
    $end_N = date('N',strtotime($end_date));
    in_array($end_N,array(6,7)) && $end_add = ($end_N == 7) ? 2 : 1;
    $alldays = abs(strtotime($end_date) - strtotime($start_date))/86400 + 1;
    $weekend_days = floor(($alldays + $start_N - 1 - $end_N) / 7) * 2 - $start_reduce + $end_add;
    if ($is_workday){
        $workday_days = $alldays - $weekend_days;
        return $workday_days;
    }
    return $weekend_days; 
}

//echo get_weekend_days('2011-06-26', '2011-07-05', true);
?>
